In a previous post, I pointed out that the evidence from twin studies strongly suggests that genes exert more influence as people get older—not less, as you might expect—and that in my own case the effect was particularly notable. But however that may be, in today’s world genes certainly count for more than they ever have, and for a number of very good reasons.
First, there is the point I made in my earlier post: choice of occupation, life-style, and social environment. In primal hunter-gatherer societies (which accounted for the vast majority of human evolutionary history) there was no division of labour beyond that between the sexes and between adults and children, and everyone had very much the same life-style. Today, however, the division of labor has reached unprecedented levels of elaboration, and life-style choices now even extend to sexual and family life. This gives enormous force to my point about individuals seeking out environments which suit their genomes. Now even homosexuals can choose congenial environments for work, leisure, and residence. This means that to the extent that homosexuality is genetic (and there is a lot of evidence that it is, at least in the case of many males) the genes in question are now being given scope for expression in males in a way they seldom if ever were in the past. And, as my earlier posts suggested, the same is true of many other genetically-determined character traits, cognitive tendencies, and sexual leanings. Indeed, even autistics can find fulfillment in many occupations thanks to today’s highly technological, diversified society; and in an earlier post I also pointed out the crucial social role that many high-functioning psychotics might play in today’s world.
Equal opportunities and increasing social equality in certain respects means that a person’s innate qualities count for more than they may have done in the past. This is demonstrably so in the case of intelligence and education. In 1930, Ivy League graduates had IQs just over 1 standard deviation (SD) above the population mean. By 1990 it was almost 2.7 SDs above, and as Herrnstein and Murray pointed out, “when a society makes good on the ideal of letting every youngster have equal access to the things that allow cognitive ability to develop, it is in effect driving the environmental component of IQ variation closer and closer to nil.” But of course by the same reasoning it is also driving the genetic factor closer and closer to being the dominant one, and what is true of IQ in particular is also likely to be generally true of other cognitive skills and abilities.
A particularly important aspect of all this is so-called assortative mating: the finding that people tend to be attracted to partners who are like themselves in some way (物以类聚，人以群分). This definitely seems to be part of the explanation of the notable increase in autism seen in places like Silicon Valley (Santa Clara County, California). In 1993 there were 4,911 diagnosed cases of autism. In 1999 the figure passed 10,000, and in 2001 there were 15,441 cases, with new ones added at 7 per day, 85 per cent of them children. Furthermore, such hot-spots for autism are not limited to California: comparable findings are reported from the Cambridge area in England. Asperger's syndrome is sometimes called "the engineer's disorder," and there is good statistical evidence linking engineering, science, and maths skills to autism. Given that employment in Silicon Valley and around Cambridge is primarily in electronic engineering and computing, and that equal-opportunity employment means that many children born there will have both parents in these industries, assortative mating has been suggested as the most likely explanation. Effectively, it is concentrating the genetic predisposition to autism from both parents in any child they may have. And of course, what is true of autistic tendencies is likely to be true of many others to the extent that they, like autism, are primarily genetic in origin. Free choice of a mate—definitely much more possible in today’s world of internet dating, international travel, and globalization—is thus another of those factors which don’t appear to be promoting the influence of genes, but almost certainly is—and demonstrably so in some places like Silicon Valley.
Finally, there is increasing survival and life-expectancy. Today many people with genetic constitutions which would have fated them to an early death or incapacitating disability in previous epochs survive to live profitable and rewarding lives. Indeed, many of them now have children of their own, and inevitably not only express, but pass on genes which would have been selected out in the past. Furthermore, if genes exert more influence the longer a person lives, it follows that increasing life-expectancy will favour increasing expression of people’s genetic endowment—a contrast that is particularly striking if you compare present-day life-expectancy in industrial societies (70-80) with the probable norm of primal hunter-gatherers (40-50): a difference not of years, but of decades. Indeed, the fact that life-expectancy continues to rise constantly in industrial societies means that this effect is likely to become more significant as time goes by, particularly when combined with the other factors described above.
All this is richly ironic in view of the fact that another characteristic of modern society (at least in the West) is the denial, disputing, and disparagement of genetic influence—notoriously so in the case of ethnic, sexual, and cognitive differences. But if the expression rather than just the inheritance of genes is also taken into account the truth is very different, and the modern world has given DNA a greater voice in human affairs than it has ever had in the past. Far from canceling out genetic influence as they are usually regarded as doing, freedom of choice, equal opportunities, and increased survival and longevity all in fact do the exact opposite and make genes rather than the environment the dominant developmental force in modern society.
